To evaluate an individual's speaking proficiency, an assessment may elicit spontaneous speech (i.e., speech that has not been prepared prior to the assessment) from the individual. Example test items that elicit spontaneous speech from test-takers include the independent and integrated items in the Test of English as a Foreign Language (TOEFL) iBT test, the Retell Lecture item in the Pearson Test of English Academic, and the oral interview in the International English Language Testing System (IELTS) Academic assessment. With the increased emphasis on complex linguistic skills in these tests and the fact that high-stakes decisions can be made based on an individual's test score, there is a possibility that a test-taker's spoken response will contain “prepared” (i.e., “canned”) material drawn from an external source. Such prepared material may be plagiarized from various sources (e.g., sources on the Internet, test preparation materials, etc.). Therefore, there is a need to detect spoken responses that are plagiarized to prevent this type of cheating strategy.